Filters, and in particular, water filters, are widely used in domestic and commercial settings to filter out impurities in fluids, such as potable water, body fluids, e.g. blood, chemicals and/or water used in high-cleanliness applications e.g. medical applications. Depending on how much fluid or water is needed, and/or whether the fluid or water is supplied from a mains supply or a tank, the fluid can either be filtered batch-wise, or continuously.
In situations where a large volume of fluid needs to be filtered, or where the fluid flow rate is relatively high, it is often more convenient to use a plumbed-in, continuous filtration system. Such systems are relatively well-known and generally comprise a filtration vessel comprising an inlet aperture connected to the supply of fluid and an outlet aperture connected to a tap or device using the filtered fluid. Contained within the filtration vessel, a filter medium is generally provided that is sealingly interposed between the inlet aperture and outlet aperture in a manner that only allows fluid to flow out through the outlet aperture once it has passed through the filtration medium.
Various filtration media can be used depending on the size and chemistry of the impurities that need to be removed from the fluid/water supply. In fact, the filter system may comprise a series of filters that successively filter out different sizes and/or types of impurities. Such, so-called multi-stage filters can be contained in a single unit, or a series of filters can be used sequentially in a given fluid/water supply.
Known filtration media include resins, scrims, reticulated sheets, porous membranes and indeed porous block media, such as compressed activated carbon blocks.
In use, filters need to be replaced periodically once the filter medium has become clogged with filtered-out impurities, or where there is a risk of biological growth over extended periods of time. For the sake of convenience, and to reduce the likelihood of incorrect servicing, it has become customary for the filter vessel and filter medium to be formed as a single disposable filter cartridge that can be clipped into and out of the supply. Such known cartridges generally comprise proprietary connectors that prevent, or reduce the likelihood of, incorrect installation thereby reducing the likelihood of contaminating the fluid or water supply, e.g. by fitting a filter with the inlet and outlet apertures reversed.
A major drawback of known disposable filter cartridges is the fact that they are comprised of various materials, e.g. a plastics vessel, rubber seals, a carbon block etc., which can make recycling of the cartridges at the end of their useful life difficult and costly. It has been proposed to replace only the filter medium, rather than the entire canister, to alleviate this problem but this solution has not been well-received owing to the fact that the remaining parts of the filter cartridge need to be thoroughly cleaned and reassembled before they can be put back into service. Moreover, a factory-sealed unit, rather than one that requires end-user intervention, is generally considered to be less susceptible to incorrect assembly, and can be monitored and/or checked at each stage of the manufacture, transport, installation and disposal cycle.